1.
/**
 * FWP, Ausgewählte Probleme aus dem ACM Programming Contest, WS10/11 
 * Problem: 10078 The Art Gallery
 * Link: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=12&page=show_problem&problem=1019
 * 
 * @author Fabian Liebl
 * @version 1.0, 10/06/2010
 * 
 * Method : Vector Algebra
 * Status : Accepted
 * Runtime: 0.120
 */

import java.io.*;

public class Main {
	
	public static void main(String[] args) throws IOException {
		BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));
		
		int points = Integer.parseInt(inputReader.readLine());
		String[] line;
		
		int[] x;
		int[] y;
		
		int v1X;
		int v1Y;
		int v2X;
		int v2Y;
		
		int dir;
		
		boolean noCrit;
		
		int turndir;
		
		while (points > 0) {
			x = new int[points];
			y = new int[points];
			noCrit = true;
			dir = 0;
			
			for (int i = 0; i < points; i++) {
				line = inputReader.readLine().split(" ");
				x[i] = Integer.parseInt(line[0]);
				y[i] = Integer.parseInt(line[1]);
			}
			
			for (int i = 0; i < points; i++) {
				// Vector i -> i+1
				v1X = x[(i + 1) % points] - x[i];
				v1Y = y[(i + 1) % points] - y[i];
				
				// Vector i -> i+2
				v2X = x[(i + 2) % points] - x[i];
				v2Y = y[(i + 2) % points] - y[i];
				
				// Direction
				turndir = v1Y*v2X - v1X*v2Y;
				
				if (turndir > 0) {
					if (dir >= 0) {
						dir = 1;
					} else {
						noCrit = false;
						break;
					}
				} else {
					if (dir <= 0) {
						dir = -1;
					} else {
						noCrit = false;
						break;
					}
				}
			}
			
			if (noCrit) {
				System.out.println("No");
			} else {
				System.out.println("Yes");
			}
			
			points = Integer.parseInt(inputReader.readLine());
		}
	}

}